Commit 2021-10-13 12:04 04ed867a

chore(topology/uniform_space/cauchy): add a few simple lemmas (#9685)

• rename cauchy_prod to cauchy.prod;
• add cauchy_seq.tendsto_uniformity, cauchy_seq.nonempty, cauchy_seq.comp_tendsto, cauchy_seq.prod, cauchy_seq.prod_map, uniform_continuous.comp_cauchy_seq, and filter.tendsto.subseq_mem_entourage;
• drop [nonempty _] assumption in cauchy_seq.mem_entourage.